Showing 28 results for Kinetic
A. Bahrami, F. Kazemi, J. Abdolahi Sharif,
Volume 17, Issue 1 (3-2020)
Abstract
Kinetic models are the most important instruments for predicting and evaluating the performance of flotation circuits. To determine the kinetic order and rate of flotation of a gilsonite sample, flotation experiments were carried out in both rougher and cleaner stages. Experiments conducted using the combinations of petroleum-MIBC, gas oil-pine oil, and one test without any collector and frother. Five first order kinetic models were applied to the data obtained from the flotation tests by using the Matrix Laboratory software. Statistical analysis showed that the classic first order model perfectly matched the rougher and cleaner results performed using petroleum-MIBC combination. The kinetic constants (k) were calculated as 0.04 (s-1) and 0.01 (s-1) for the rougher and cleaner, respectively. Rougher and cleaner tests without collector and frother also matched with the modified gas/solid adsorption and rectangular models with the k values of 0.05 (s-1), and 0.01 (s-1), respectively. The relationship between flotation rate constant, maximum combustible recovery and particle size were also studied. The results showed that the maximum flotation combustible recovery and flotation rate were obtained with an intermediate particle size both in the rougher and cleaner flotation processes. The combustible recovery and flotation rate in the rougher flotation process were higher than that in the cleaner flotation process.
E. Shahmohamadi, A. Mirhabibi, F. Golestanifard,
Volume 17, Issue 1 (3-2020)
Abstract
In the present study, a soft computing method namely the group method of data handling (GMDH) is applied to develop a new and efficient predictive model for prediction of conversion percentage of silicon. A comprehensive database is obtained from experimental studies in literature. Several effective parameters like time, temperature, nitrogen percentage, pellet size and silicon particle size are considered. The performance of the model is evaluated through statistical analysis. Moreover, the silicon nitridation was performed in 1573 k and results were evaluated against model results for validation of the model. Furthermore, the performance and efficiency of the GMDH model is confirmed against the two most common analytical models. The most effective parameters in estimating the conversion percentage are determined through sensitivity analysis based on the Gamma Test. Finally, the robustness of the developed model is verified through parametric analysis.
A. Kazazi, S. M. Montazeri, S. M. A. Boutorabi,
Volume 17, Issue 4 (12-2020)
Abstract
In the present study, austempering heat treatment was performed on compacted graphite aluminum cast iron with the chemical composition of 4.8%wt Al, 3.2%wt C, 0.81%wt Ni, 0.37%wt Mn, and 0.02%wt Mg. This study aims to investigate the effect of aluminum additions and removal of silicon on the kinetics of austempering transformation of Fe-3.2%C alloy. The cast samples were austenitized at 900 °C for 120 min and the isothermal austempering heat treatment was performed at 200 °C, 300 °C and 400 °C for 5, 30, 60, 120 and 180 minutes, respectively. Kinetics of this transformation was studied by X-Ray diffraction (XRD) analysis. The effect of temperature and time on the microstructure and hardness of the austempered samples was investigated and discussed. The presence of Al was seen to prolonged formation of the carbides from high carbon austenite, and that expanded the process window in the austempering transformation. Besides, the lower bainitic ferrite phase was observed in the austempered samples at 200 °C and 300 °C. Increasing austempering temperature to 400 °C changed the lower bainite to upper bainite structure. The volume fraction of austenite reached its maximum level (34.6 %) after austempering the samples at 400 °C for 30 minutes.
Shadi Moshayedi, Hossein Sarpoolaky, Alireza Khavandi,
Volume 19, Issue 2 (6-2022)
Abstract
In this paper, chemically-crosslinked gelatin/chitosan hydrogels containg zinc oxide nanoparticles (ZNPs), were loaded with curcumin (CUR), and their microstructural features, physical properties, curcumin entrapment efficiency, and drug release kinetics were evaluated using scanning electron microscopy (SEM), the liquid displacement method, and UV–Vis spectroscopy. The in vitro kinetics of drug release was also studied using First-order, Korsmeyer-Peppas, Hixon-Crowell, and Higuchi kinetic models. The SEM micrographs confirmed the formation of highly porous structures possessing well-defined, interconnected pore geometries. A significant reduction in the average pore sizes of the drug-loaded hydrogels was observed with the addition of ZNPs and CUR to the bare hydrogels. High value of drug loading efficiency (~ 72 %) and maximum drug release of about 50 % were obtained for the drug-loaded scaffolds. It was found that curcumin was transported via the non-Fickian diffusion mechanism. It was also shown that the kinetics of curcumin release was best described in order by Hixon-Crowell, Higuchi, and Korsmeyer-Peppas models, demonstrating that drug release was controlled by diffusion, degradation, and swelling of the drug carrier. However, lower degree of fitting was observed with First-order kinetic model.
Yaser Moazzami, Mahdi Gharabaghi, Ziadin Shafaei Tonkaboni,
Volume 19, Issue 4 (12-2022)
Abstract
Ionic liquids as green solvents with high thermal stability, recyclability, low flash point, and low vapor
pressure, have been considered as a viable alternative in hydrometallurgical processes. In this study the leaching
kinetics of chalcopyrite concentrate was investigated using 1-Butyl-3-methylimidazolium hydrogen sulfate
(BmimHSO4) as an acidic ionic liquid. The Effect of operational parameters, including temperature, BmimHSO4
concentration, H2O2 concentration, stirring speed, solid-to-liquid ratio, and particle size on the rate of copper
dissolution of CuFeS2 were examined systematically. The highest Cu efficiency (ca. 97%) was achieved using 40%
(w/v) BmimHSO4, 30 %v/v H2O2, and 10 g.L-1 solid to liquid ratio for particle sizes less than 37 μm at 300 rpm and
45°C after 180 min leaching time. Kinetics study using Shrinking Core Model (SCM) revealed that CuFeS2 leaching
process using BmimHSO4 follows chemical reaction-controlled process. Under these circumstances, the calculated
activation energy was 46.66 KJ/mol. Moreover, the orders of reaction with respect to BmimHSO4 and H2O2
concentration, solid to liquid ratio and particle size were estimated to be 0.539, 0.933, −0.676 and −1.101
respectively. The obtained Arrhenius constant was found to be 0.26 106. The calculation of apparent activation
energy using “time given to a fraction method” revealed that the leaching mechanism remains the same over the
course of time.
Chouchane Toufik, Sana Chibani, Ouahida Khireddine, Atmane Boukari,
Volume 20, Issue 1 (3-2023)
Abstract
In this work, blast furnace slag (BFS) was used as an adsorbent material for the removal of Pb(II) ions in solution in batch mode. The physico-chemical analyzes used indicated that the BFS is essentially composed of silica, lime, and alumina. Its specific surface area corresponds to 275.8m2/g and its PZC is around 3.8.
The adsorption study indicated that the maximum amount of Pb(II) adsorbed under optimum conditions (agitation speed (Vag): 150rpm; pH: 5.4; particle size (Øs): 300µm, T: 20°C) is 34.26mg/g after 50 minutes of agitation, and adsorption yield is best for feeble initial concentrations. The most appropriate isothermal model was that of Langmuir, and the adsorption speed was better characterized by the pseudo-second order kinetic model. The adsorption mechanism revealed that internal diffusion is not the only mechanism that controls the adsorption process; there is also external diffusion, which contributes enormously in the transfer of Pb(II) from solution to adsorbent. Thermodynamic study indicated that the Pb(II) adsorption on the blast furnace slag (BFS) was spontaneous, exothermic, and that the adsorbed Pb(II) is more ordered at the surface of the adsorbent. Finally, we estimate that BFS is a superb adsorbent for water containing Pb(II).
Mohammad Javad Sohrabi, Hamed Mirzadeh, Saeed Sadeghpour, Reza Mahmudi,
Volume 20, Issue 4 (12-2023)
Abstract
Deformation-induced α΄-martensite generally forms at shear bands in the coarse-grained austenite, while it nucleates at grain boundaries in the ultrafine-grained (UFG) austenite. The available kinetics models are related to the nucleation on the shear band intersections, and hence, their application to investigating the kinetics of α΄-martensite formation for the UFG regime cannot be justified. Accordingly, in the present work, the general Johnson–Mehl–Avrami–Kolmogorov (JMAK-type) model was implemented for comparing the kinetics of α΄-martensite formation in the UFG and coarse-grained regimes using an AISI 304L stainless steel. On the experimental front, the X-ray diffraction (XRD) patterns and the electron backscattered diffraction (EBSD) maps were used for phase and microstructural analyses, respectively. It was revealed that the simple JMAK-type model, by considering the dependency of the volume fraction of α΄-martensite on the strain, is useful for modeling the experimental data, predicting the nucleation sites based on the theoretical Avrami exponents, and characterizing the transformation kinetics at low and high strains.
Dewi Qurrota A'yuni, Hadiantono Hadiantono, Velny Velny, Agus Subagio, Moh. Djaeni, Nandang Mufti,
Volume 21, Issue 3 (9-2024)
Abstract
Rice husk carbon by-product from the industrial combustion is a promising source to produce a vast amount of activated carbon adsorbent. This research prepared rice husk-activated carbon adsorbent by varying the concentration of potassium hydroxide solution (5, 10, 15, 20 % w/v) and activation time (2, 4, 6, 8 hours). Fourier-transform infrared spectral characterization (FTIR) indicated a significant effect before and after activation, especially the presence of hydroxyl groups. Based on the iodine adsorption, the specific surface area of the produced-activated carbon was approximately 615 m2/g. Experimental results showed that increasing potassium hydroxide concentration and activation time increases the water vapor adsorption capacity of the activated carbon. Compared with the rice husk carbon, the KOH-activated carbon enhanced the water vapor adsorption capacity to 931%. In the adsorption observation, changing the temperature from 15 to 27 ℃ caused a higher water vapor uptake onto the activated carbon. Two adsorption kinetics (pseudo-first- and pseudo-second-order models) were used to evaluate the adsorption mechanism. This research found that rice husk-activated carbon performed a higher water vapor adsorption capacity than other adsorbents (silica gel, zeolite, and commercially activated carbon).
